I would like to explicate this sentence in the op-ed:
In a polarized time, the filibuster tends to make Senate actions more representative of the nation as a whole.
Here’s the reasoning behind that conclusion. Assume the electorate forms a normal distribution with regard to policy preferences. Normally both parties would compete to attract the vote of the median voter thereby winning an election. In a polarized time for whatever reason, both parties might have programs some distance from the median voter. If a governing party acted on such non-median preferences, the resulting law would ignore the wishes of a substantial number of voters in the middle or “thick” part of the distribution. A filibuster would either 1) prevent a law from passing or 2) force a majority to accommodate the views of the most right- or left- leaning legislators in the minority party. The views of the legislators required by the filibuster would presumably reflect the views of many voters in the thick part of the distribution. In this way, the filibuster would require laws to become closer to what a majority wanted than the laws that a filibuster-free majority would have passed.
Of course, with regard to the theory, it makes no sense that polarization would exist to begin with: if either party varied from the wishes of the median voter, the other would swoop in and pick up those votes. However, polarization exists so I assume both parties govern somewhat off the median.